UT - Plano Concave Lens Confusion

Hi, I was reading the study guide for UT-L3. In chapter 2, it says that Immersion testing, the sound beam can be focused using plano-concave lenses. I was looking through the Google images and found that it is the plano convex lenses that give a focus. Can someone clear my understanding?

If you want to learn more, please visit our website.

10:24 Sep-01-

https://www.ndt.net/forum/thread.php?msgID=#

Re: UT - Plano Concave Lens Confusion 10:24 Sep-01-In Reply to Rey at 20:44 Aug-31- (Opening).

The situation in acoustics is different than in optics: light speed is lower in glass than in the air and sound speed in practically each solid material is higher than in fluid. Plano concave lens allows to focus sound waves in fluids. Additional significant difference between optics and acoustics is the fact, that material impedances can vary very significantly in acoustics (many thousand times) and only minor differences are observed in optics. And naturally everybody working with sound waves must know, that this are coherent waves with practically unlimited coherence time. And may be the last difference between optics and acoustics: sound waves in typical materials are not undergoing dispersion that is typical for light waves.

Link to Hongsheng

• Company: Shanghai Optics Inc.
• Type: Lenses
• Lens Category: Spherical Lens
• Applications: Astronomy, Biomedical/Medical, Industrial, Military, Scientific Research
• Shape: Plano Concave
• Dimension Tolerance: +/-0.05mm
• Center Thickness Tolerance: +/-0.05 mm
• Radius Tolerance: +/-0.3%
• Surface Quality (S/D): 40-20
• Centration(arc min): 3&#;

A plano concave lens is an optical lens with one concave surface and one flat surface. It has a negative focal length, and can be used for light projection, beam expansion, or to increase focal length of an optical system. We produce lenses from 2.33 mm to mm in diameter; coated/uncoated options, and our design engineers can work with you to design custom lenses to fit your applications.

A plano concave lens is an optical lens with one concave surface and one flat surface. It has a negative focal length, and can be used for light projection, beam expansion, or to increase focal length of an optical system. We produce lenses from 2.33 mm to mm in diameter; coated/uncoated options, and our design engineers can work with you to design custom lenses to fit your applications.